Definitely dust, and definitely plenty of it. Clouds stirred into the air and stayed suspended as they moved deeper, wafting between them in the faintest breaths of air: a warm autumn breeze that smelled like decay, laden with the sweetness of the dying season. In the little moonlight that shafted into the hall the dust glittered in eddies --

And behind them, in more purposeful swirls, spinning and building into a figure, indistinct and barely-visible in the shadowy hall, lurching after them in a silent awkward hunch.